What this calculator does

Fuel is delivered to an aircraft in litres from a fuel truck, but flight planning, weight and balance, and the aircraft's own fuel quantity indication work in kilograms. The truck meter and the aircraft gauges therefore never agree directly: the litres pumped have to be converted through the fuel's density before they can be compared with the change in the aircraft's fuel weight. This calculator does that comparison and shows how far the two figures are apart, in US gallons, so a fuel receipt can be checked against what actually went into the tanks.

Inputs

• Truck Meter (L) — the volume of fuel delivered according to the fuel truck's meter, in litres.
• Fuel Density — the density printed on the fuel receipt. Enter it in kg per litre (typical Jet A-1 values are 0.775–0.840 kg/L) or, using the switch, in kg per US gallon.
• Before (KG) — the aircraft's total fuel on board before refuelling, from the fuel quantity indication.
• After (KG) — the aircraft's total fuel on board after refuelling.

How the numbers are worked out

• Fuel density in the other unit — kg/L × 3.78 gives kg/US gal (1 US gallon is 3.785 litres); kg/US gal ÷ 3.78 goes the other way.
• Calculated added fuel (KG) — After minus Before: the weight of fuel the aircraft says it received.
• Calculated added fuel (US GAL) — the added weight divided by the density in kg/US gal: the volume the aircraft says it received.
• Truck meter (US GAL) — the litres on the truck meter × 0.264: the volume the truck says it delivered.
• Difference (US GAL) — the gap between those two volumes.
• Tolerance (US GAL) — 3% of the calculated added fuel plus 100 gallons. A difference inside this allowance is normal gauge and meter error; a difference outside it should be investigated before the fuel receipt is accepted.

Worked example

Truck meter 12,000 L, density 0.800 kg/L, 5,000 kg before and 12,500 kg after. Density becomes 0.800 × 3.78 = 3.024 kg/US gal. Added fuel is 7,500 kg, or 7,500 ÷ 3.024 = 2,480 US gal. The truck meter reads 12,000 × 0.264 = 3,168 US gal. The difference is 688 gallons against a tolerance of 3% × 2,480 + 100 = 174 gallons, so this uplift would be flagged for a second look.

Notes

• Results are rounded to whole gallons; density is shown to three decimals.
• The conversion factors are rounded (3.78 and 0.264), which is adequate for a ramp check but not for a legal fuel reconciliation. Use your operator's published figures where they differ.
• Nothing you enter leaves your browser; the calculation runs entirely on this page.